The invention relates to a fiber guide channel for the pneumatic transport of individual fibers, such as are combed out of a feed sliver by an opening cylinder that rotates in an opening cylinder housing of an open end spinning device for delivery to a spinning rotor.
Fiber guide channels of this type are known in connection with open end spinning devices from numerous publications.
German Patent Publication DE 195 11 084 A1 describes, for example, an open end spinning device with a sliver opening mechanism, in which a sliver temporarily stored in a spinning can, as conventional, is fed to a rotating opening cylinder, which opens the sliver into individual fibers. The individual fibers are then fed onto a spinning rotor running at a high speed in a rotor housing, via a fiber guide channel, where they are continuously rotated, in an inner rotor groove, onto the end of a yarn leaving the spinning rotor via a withdrawal nozzle. The finished yarn is then wound to form a cross-wound bobbin on an associated winding mechanism.
High demands are placed on the designs of fiber guide channels of this type, in this case, for example with regard to the geometric configuration. In other words, the flow conditions inside the fiber guide channels have to ensure that the fibers are stretched during transport or are at least kept stretched. Moreover, the surface of these components must be continuously smooth, so no fibers attach to the wall during the pneumatic transport. Moreover, harmful air vortexes forming in the boundary layer region of the fiber guide channels should be avoided as far as possible.
A comparable fiber guide channel is also described in German Patent Publication DE 197 12 881 A1. In this known mechanism, the opening cylinder housing is connected pneumatically to the spinning rotor via a multi-part fiber guide channel. This means that the fiber guide channel consists of two separate channel portions, namely a channel portion running inside a so-called fiber guide channel insert and a channel portion arranged in a channel plate adapter. During operation, in other words when the rotor housing is closed, the channel plate adapter, which, apart from the opening region of the fiber guide channel, also has a bore for fixing a thread withdrawal nozzle, extends into the running spinning rotor. It is thus ensured that the opening region of the fiber guide channel is positioned adequately closely to the fiber slide wall of the spinning rotor, so the individual fibers transported in the fiber guide channel are fed according to regulations onto the spinning rotor.
As can be seen from the two patent applications described above, the fiber guide channels have an inlet opening, the width of which is matched to the width of the opening roller mountings. In order to achieve a stretching of the fibers by acceleration of the transport air flow, the free cross-sectional area of fiber guide channels of this type is moreover generally selected in such a wav that it decreases in the direction of the outlet opening of the fiber guide channel. The outlet opening, in this case, substantially has a circular cross-section, the minimum diameter of which is predetermined by the air and fiber throughput required during spinning. The fibers are, in this case, fed onto a relatively wide region of the fiber slide wall of the spinning rotor. Fibers, which are fed onto the fiber slide face in the edge region of the spinning rotor, during their transport to the fiber collecting groove, where they are bound into the thread, are accelerated and further stretched by the rotor rotation and the centrifugal force caused thereby. Fibers, which are fed on near the rotor groove, receive significantly lower stretching, resulting in a different degree of stretching and overall reduced substance utilization with regard to the specific strength of the yarn produced.
Apart from fiber guide channels with round outlet openings, fiber guide channels with an elongate outlet opening extending substantially in the direction of the rotor periphery are also prior art.
German Patent Publication DE-OS 19 39 760 describes, for example, an open end spinning device with a fiber guide channel, which connects an opening cylinder and a spinning rotor. The fiber guide channel, in this case, may have various cross-sectional shapes, for example rectangle, trapezium etc., in particular. also in the region of the outlet opening. In principle, the channel shape from the inlet at the opening cylinder to the opening in the spinning rotor is substantially unchanged. The fibers conveyed in this fiber guide channel, for this reason, are conveyed as far as possible in the position and spread up to the fiber slide face of the spinning rotor in which they arrive from the opening cylinder into the fiber guide channel.